Biosensor with a sensing surface on an interlayer dielectric

ABSTRACT

The present disclosure relates to an integrated chip having an integrated bio-sensor having horizontal and vertical sensing surfaces. In some embodiments, the integrated chip has a sensing device disposed within a semiconductor substrate. A back-end-of the line (BEOL) metallization stack with a plurality of metal interconnect layers electrically coupled to the sensing device is arranged within an inter-level dielectric (ILD) layer overlying the semiconductor substrate. A sensing well is located within a top surface of the ILD layer. The sensing well has a horizontal sensing surface extending along a top surface of a first one of the plurality of metal interconnect layers and a vertical sensing surface extending along a sidewall of a second one of the plurality of metal interconnect layers overlying the first one of the plurality of metal interconnect layers. The use of both horizontal and vertical sensing surfaces enables more accurate sensing.

BACKGROUND

In recent years, the semiconductor industry has developed integrated chips (ICs) having integrated bio-sensors configured to detect the presence of certain biomarkers in an ambient environment (e.g., a patient's blood stream). These bio-sensors take advantage of the selective interaction and binding of certain biological receptors to identify and detect different analytes such as toxins, hormones, DNA strands, proteins, bacteria, etc., in a variety of applications such as molecular diagnostics, pathogen detection, and environmental monitoring.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 illustrates some embodiments of a cross-sectional view of an integrated chip comprising an integrated bio-sensor having sensing well with horizontal and vertical sensing surfaces.

FIGS. 2a-2b illustrate some alternative embodiments of an integrated chip comprising an integrated bio-sensor having sensing well with horizontal and vertical sensing surfaces.

FIGS. 3a-3b illustrates some embodiments of an integrated chip comprising an array of sensing wells that is operable to detect different analytes.

FIGS. 4-8 illustrate some alternative embodiments of cross-sectional views of an integrated chip comprising an integrated bio-sensor having sensing well with horizontal and vertical sensing surfaces.

FIG. 9 illustrates a flow diagram of some embodiments of a method of forming an integrated chip comprising an integrated bio-sensor having sensing well with horizontal and vertical sensing surfaces.

FIGS. 10-17 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising an integrated bio-sensor having sensing well with horizontal and vertical sensing surfaces.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Integrated bio-sensors typically comprise a conductive horizontal sensing surface that is disposed within a top metal interconnect layer of an integrated chip back-end-of-the-line (BEOL) metal stack, and which is electrically coupled to a sensing device disposed within an underlying semiconductor body. A polymer material is disposed over the top metal interconnect layer to form a sensing well configured to act as a receptacle for a liquid to be analyzed. During operation, analytes from the liquid will vary electrical operation of the sensing device, indicating a presence of the analyte in the liquid.

It has been appreciated that the sensitivity of an integrated bio-sensor is proportionate to the surface area of the conductive sensing surface. However, the flat geometry of a horizontal sensing surface practically limits the size of the surface area (e.g., since the high cost of silicon real estate on a wafer limits a size of an integrated bio-sensor), thereby limiting the ability of an integrated bio-sensor to detect an analyte.

Accordingly, the present disclosure relates to an integrated chip comprising an integrated bio-sensor having horizontal and vertical sensing surfaces. In some embodiments, the integrated chip comprises a sensing device disposed within a semiconductor substrate. A back-end-of the line (BEOL) metallization stack comprising a plurality of metal interconnect layers electrically coupled to the sensing device is disposed within an inter-level dielectric (ILD) layer overlying the semiconductor substrate. A sensing well is located within a top surface of the ILD layer. The sensing well comprises a horizontal sensing surface extending along a top surface of a first one of the plurality of metal interconnect layers and a vertical sensing surface extending along a sidewall of a second one of the plurality of metal interconnect layers overlying the first one of the plurality of metal interconnect layers. The use of both horizontal and vertical sensing surfaces increases the total area of the sensing surface. The increased sensing area enables more accurate sensing (e.g., high sensitivity and high signal response), and can also provide for an optimum ratio of a sensing surface to a volume of the sensing well for detection of specific analytes (i.e., bio-targets).

FIG. 1 illustrates some embodiments of a cross-sectional view of an integrated chip 100 comprising an integrated bio-sensor 101 having a sensing well with horizontal and vertical sensing surfaces.

The integrated bio-sensor 101 comprises a sensing device 104 disposed within a semiconductor substrate 102. The sensing device 104 is electrically coupled to a back-end-of-the-line (BEOL) metallization stack 108 comprising a plurality of metal interconnect layers, C0-M4, disposed within an inter-level dielectric (ILD) layer 106 having one or more dielectric materials. In some embodiments, the BEOL metallization stack 108 may comprise a conductive contact CO configured to connect the sensing device CO to one or more overlying metal wires Mx (x=1, 2, 3, 4) vertically interconnected by way of one or more metal vias Vx (x=1, 2, 3). In some embodiments, the conductive contact CO and the metal vias Vx may comprise tungsten or copper, while the metal wire Mx may comprise copper or aluminum.

The ILD layer 106 comprises a sensing well 112 disposed within a top surface 106 t of the ILD layer 106. The sensing well 112 comprises a cavity or negative relief within the top surface 106 t of the ILD layer 106. A sensing enhancement layer 110 is disposed onto interior surfaces of the sensing well 112. In some embodiments, the sensing enhancement layer 110 may also extend along the top surface 106 t of the ILD layer 106. The sensing enhancement layer 110 may comprise a high-k dielectric layer configured to enhance electrical interaction between analytes within a sample (e.g., a liquid) and the plurality of metal interconnect layers, C0-M4.

The sensing well 112 comprises a horizontal sensing surface 112 h and one or more vertical sensing surfaces 112 v. The horizontal sensing surface 112 h runs along a middle metal wire layer M3 (i.e., a metal wire layer having overlying metal layers) extending in a lateral direction within the BEOL metallization stack 108. The one or more vertical sensing surfaces 112 v run along sidewalls of one or more overlying metal interconnect layers, V3 and M4, within the BEOL metallization stack 108. For example, metal wire layer M3 runs along a bottom surface of the sensing well 112 to form a horizontal sensing surface 112 h, while metal via layer V3 and overlying metal wire layer M4 run along one or more sidewalls of the sensing well 112 to form vertical sensing surfaces 112 v.

The use of the vertical sensing surfaces 112 v, in addition to the horizontal sensing surface 112 h, increases the total area of the sensing surface relative to bio-sensors that do not have vertical sensing surfaces. The increased sensing area gives more chance for the integrated bio-sensor 101 to sense an analyte (i.e., to generate more charge from ions, photons, or any charge inducted sources in an liquid), thereby enabling more accurate sensing (e.g., high sensitivity and high signal response).

FIGS. 2a-2b illustrate some alternative embodiments of an integrated chip 200 comprising an integrated bio-sensor having a sensing well 214 with horizontal and vertical sensing surfaces.

As shown in FIG. 2a , the integrated chip 200 comprises a sensing device 202 disposed within a semiconductor substrate 102. In some embodiments, the sensing device 202 may comprise a MOSFET device having a source region 202 a and a drain region 202 b laterally separated by a channel region 202 c. A gate region 202 d is vertically separated from the channel region 202 c by way of a gate dielectric layer 202 e (e.g., a silicon dioxide (SiO₂) layer).

The gate region 202 d of the semiconductor device is electrically coupled to one or more lower metal layers C0-V2, disposed within a first ILD material 204 in a BEOL metallization stack 203. In some embodiments, the first ILD material 204 may comprise one or more different ILD layers. A middle metal wire layer M3 is disposed over and is connected to the one or more lower metal layers C0-V2. In various embodiments, the middle metal wire layer M3 may be disposed within the first ILD material 204 or within a different, second ILD material 206 overlying the first ILD material 204. One or more upper metal layers V3-M4 are disposed over and are electrically connected to the middle metal wire layer M3. In some embodiments, the one or more upper metal layers V3-M4 may be disposed within the second ILD material 206. In various embodiments, the first ILD material 204 and the second ILD material 206 may comprise a same dielectric material or different dielectric materials. For example, in some embodiments, the lower one or more lower metal layers C0-V2 may comprise thin metal layers disposed within a low-k or an extreme low-k dielectric material, while the middle and/or upper metal layers M2 and/or V3-M4 may comprise a thicker metal layers disposed within a silicon dioxide (SiO₂) layer.

A sensing well 214 is disposed within a top surface 206 t of the second ILD material 206. The sensing well 214 extends from the top surface 206 t of the second ILD material 206 to a top surface of the middle metal wire layer M3. The middle metal wire layer M3 and the upper metal layers V3-M4 abutting the sensing well 214 are electrically coupled to the gate region 202 d, so as to form an extended gate electrode. The sensing device 202 is able to detect analytes (e.g., ion concentrations, photon concentrations, DNA sequences, etc.) based upon changes in electric potential change around the extended gate electrode (e.g., based upon a change in electric charge around the extended gate electrode determined by Poisson's equal or based upon a chemical equilibrium potential determined by the Nernest equation).

In some embodiments, a sensing enhancement layer 212 comprising a high-k dielectric material is disposed onto interior surfaces of the sensing well 214. For example, the sensing enhancement layer 212 may be disposed onto a horizontal sensing surface 214 h running along a bottom surface of the sensing well 214 and a vertical sensing surface 214 v running along sidewalls of the sensing well 214. In some embodiments, the sensing enhancement layer 212 may have thicknesses in a range of between approximately 10 angstroms and approximately 200 angstroms along the horizontal and vertical sensing surfaces, 214 h and 214 v. In some embodiments, the sensing enhancement layer 212 may also extend along the top surface 206 t of the second ILD material 206. In various embodiments, the sensing enhancement layer 212 may comprise one or more of silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), titanium oxide (TiO₂), hafnium oxide (HfO₂), tantalum pentoxide (Ta₂O₅), tin oxide (SnO), tin dioxide (SnO₂), BaxSr₁—xTiO₃ (BST).

In some embodiments, the sensing well 214 may vertically extend along a via layer V3 and an overlying upper metal wire layer M4. In some embodiments, the sensing well 214 is disposed between two or more vias of a via array and metal wires within the upper metal layers V3-M4. In some such embodiments, the sidewalls of the sensing well 214 may comprise angled sidewalls (e.g., sidewalls having an angle Φ with respect to a normal) along the upper metal wire layer M4. In some embodiments, the sensing well 214 may comprise nooks 215 disposed within the sidewalls of the sensing well 214 at a position vertically underlying the upper metal wire layer M4.

A first capping structure 218 and a second capping structure 220 may be disposed over the semiconductor substrate 102. In some embodiments, the first capping structure 218 may be bonded to the second ILD layer 206 by way of a first adhesive layer and the second capping structure 220 may be bonded to the first capping structure 218 by way of a second adhesive layer. In some embodiments, the first capping structure 218 comprises a malleable polymer material, while the second capping structure 220 may comprise a rigid material. For example, in some embodiments, the first capping structure 218 may comprise PDMS (polydimethylsiloxane), while the second capping structure 220 may comprise quartz. In other embodiments, the first and/or second capping structures, 218 and 220, may comprise quartz and/or silicon. In some embodiments, the first capping structure 218 and second capping structure 220 may be optically transmissive (i.e., transparent). In such embodiments, reactions occurring within the sensing well 214 may be optically observed (e.g., using a microscope external to the integrated chip 200).

In some embodiments, a first side of the first capping structure 218 facing the semiconductor substrate 102 may comprise a first cavity and a second side of the first capping structure 218 opposing the semiconductor substrate 102 may comprise a second cavity. The first cavity forms a micro-fluidic channel 218 a over the second ILD material 206, which extends over the sensing well 214. The second cavity may form a chamber 222, which may be expanded to operate as a peristaltic pump and/or valve. For example, if the pressure in the chamber 222 is increased, the bottom wall of the chamber 222 will move downward, either acting as a valve (to block liquid from entering the sensing well 214) or a pump (to push liquid into the sensing well 214).

In some embodiments, the upper metal wire layer M4 may comprise one or more EWOD (electrowetting on dielectrics) electrodes, 208 a and 208 b. In some embodiments, a hydrophobic layer 216 is disposed over the sensing enhancement layer 212 at a position overlying the EWOD electrodes, 208 a and 208 b. In some embodiments, the hydrophobic layer 216 may comprise a self assembled monolayer (SAM) or a teflon material. The EWOD electrodes, 208 a and 208 b, are configured to selectively generate electric fields that are configured to modify wetting properties of the hydrophobic layer 216 to control the flow of liquid within the micro-fluidic channel 218 a. For example, the EWOD electrodes, 208 a and 208 b, may be configured to manipulate liquid drops in a manner that fills the sensing well 214. In other embodiments, the integrated chip 200 may comprise alternative droplet manipulation elements, such as light-generation elements that enable droplet manipulation by optical tweezers or electrodes that generate non-uniform electric fields to enable droplet manipulation by dielecrophoresis.

In some embodiments, the integrated chip 200 may further comprise a heating element 230. In some embodiments, the heating element 230 may be disposed within the semiconductor substrate 102. The heating element 230 may be configured to vary a temperature of a liquid within the micro-fluidic channel 218 a that is to be sampled by the sensing well 214 to enable a desired reaction within the liquid (e.g., to amplify a DNA signal by changing DNA from a double strand structure to a single strand structure). In some embodiments, a temperature sensor 228 may be disposed between the second and third capping structures, 218 and 220. In some embodiments, the temperature sensor 228 may comprise a thermal coupling element (e.g., a platinum thermocouple).

In some embodiment, the second capping structure 220 may have a first opening 224 and a second opening 226. The first opening 224 extends through the second capping structure 220 and the underlying first capping structure 218 to an underlying signal output electrode 210 within the upper metal layer M4. The first opening 224 provides an opening in which an electrical connection can be made from the integrated bio-sensor (e.g., from signal output electrode 210) to an external circuit. The second opening 226 exposes the temperature sensor 228 to an ambient environment, thereby allowing the temperature sensor 228 to measure a temperature of a liquid in the ambient environment. In some embodiments, the heating element 230 is configured to generate heat dependent upon a temperature measured by the temperature sensor 228. For example, if the temperature sensor 228 measures a first temperature of the ambient environment the heating element 230 may be operated to generate a first amount of heat, while if the temperature sensor 228 measures a second temperature less than the first temperature the heating element 230 may be operated to generate a second amount of heat greater than the first amount of heat.

FIG. 2b illustrates some embodiments of a top-view 232 of the integrated chip 200 (along line A-A′ of FIG. 2a ). As shown in top-view 232, the upper metal wire layers V3-M4 are arranged along opposing sides of the sensing well 214. By arranging the upper metal wire layer M4 along opposing sides of the sensing well 214, the total surface area of the sensing area can be increased to thereby provide for more accurate sensing. The micro-fluidic channel 218 a provides a path between an ambient environment to the sensing well 214, which provides a sample 234 to the sensing well 214. While top-view 232 illustrates the integrated bio-sensor 200 as comprises a sensing well 214 having a substantially square shape, it will be appreciated that in other embodiments, the sensing well 214 may have alternative shapes (e.g., a circular shape, an oblong shape, a triangular shape, etc.). Furthermore, while the micro-fluidic channel is illustrated as providing a path from a side of the semiconductor substrate 102 to the sensing well 214, it will be appreciated that the channel may alternatively provide a path from a top of a capping structure, 218 or 220, to the sensing well 214.

FIGS. 3a-3b illustrates some embodiments of an integrated chip comprising an array of sensing wells that is operable to detect different analytes.

FIG. 3a illustrates a cross-sectional view of some alternative embodiments of an integrated chip 300 comprising an array of sensing wells having a plurality of sensing wells, 214 a and 214 b. The plurality of sensing wells, 214 a and 214 b, are coupled to one or more micro-fluidic channels, 218 a and 218 b, which are configured to perform a multiplexing operation that provides a liquid to a first one of the sensing wells, 214 a or 214 b, without providing the liquid to a second one of the sensing wells, 214 b or 214 a. In some embodiments, cavities 222 a or 222 b may act as a valve to prevent liquid from being provided one of the sensing wells, 214 a or 214 b.

FIG. 3b illustrates a top-view 302 corresponding to integrated chip 300 (along line B-B′ of FIG. 3a ). As shown in top-view 302, the micro-fluidic channels, 218 a and 218 b, separate the array of sensing wells 304 into first and second sub-arrays, 306 a and 306 b. By using the micro-fluidic channels, 218 a and 218 b, to provide liquid to different sub-arrays, 306 a or 306 b, of sensing wells, the integrated chip 300 is able to perform multiplexing that enables the integrated chip 300 to detect different analytes. For example, during operation, a first biologically sensitive element such as a first enzyme 308 a may be introduced into sensing wells of the first sub-array 306 a by way of micro-fluidic channel 218 a. The first enzyme 308 a is immobilized onto the sensing enhancement layer of sensing wells of the first sub-array 306 a, thereby enabling the first sub-array 306 a to detect a first analyte associated with the first enzyme 308 a. Similarly, a second biologically sensitive element such as a second enzyme 308 b may be introduced into sensing wells of the second sub-array 306 a by way of micro-fluidic channel 218 b. The second enzyme 308 b is immobilized onto the sensing enhancement layer of sensing wells of the second sub-array 306 b, thereby enabling the second sub-array 306 b to detect a second analyte (different than the first analyte) corresponding to the second enzyme 308 b.

FIG. 4 illustrates some embodiments of a cross-sectional view of an integrated chip 300 comprising a disclosed integrated bio-sensor.

Integrated chip 400 comprises a sensing well 406 disposed within a top surface of the second ILD material 206. A sensing enhancement layer 404 is arranged on a horizontal sensing surface 406 h running along a bottom of the sensing well 406 and vertical sensing surfaces 406 v running along sidewalls of the sensing well 406. The vertical sensing surfaces 406 v vertically extend along multiple via layers V3, V4 and metal wire layers M3, M4 of BEOL metal stack 402. For example, the sensing well 406 has sidewalls that vertically extend along first via layer V3, a second metal layer M4, a second via layer V4 and a second metal layer M5. By extending the sidewalls of the sensing well 406 along multiple via (e.g., V3 and V4) and metal wire layers (e.g., M4 and M5), a depth d of sensing well 214 can be adjusted to improve sensing accuracy and/or to provide an optimum sensing surface to volume ratio for detection of a specific analyte (e.g., bio-target). In alternative embodiments, more or less metal layers can be added to achieve the optimum ratio. In some embodiments, the sensing enhancement layer 406 may have a thickness in a range of between approximately 10 angstroms and approximately 200 angstroms along the horizontal and vertical sensing surfaces, 406 h and 406 v. It will be appreciated that sensing enhancement layers of subsequent figures (e.g., sensing enhancement layers 504, 604, 702, 802) may have thicknesses in a substantially same range.

FIG. 5 illustrates some embodiments of a cross-sectional view of an integrated chip 500 comprising a disclosed integrated bio-sensor.

Integrated chip 500 comprises a sensing well 506 disposed within a top surface of the second ILD material 206. A sensing enhancement layer 504 may be arranged along a horizontal sensing surface 504 h running along a bottom of the sensing well 506 and vertical sensing surfaces 504 v running along sidewalls of the sensing well 506. The sensing enhancement layer 504 may have curved surfaces along the vertical sensing surfaces 504 v, which vertically extend along multiple via layers V3, V4 and metal wire layers M3, M4 of BEOL metal stack 502. In some embodiments, the curved surfaces of the vertical sensing surfaces 506 v comprises one or more arches. The arches of the vertical sensing surfaces 506 v increase the surface area of the vertical sensing surfaces 506 v, thereby increasing sensing area (and therefore increase the sensing signal) without substantially increasing the size of the bio-sensor. FIG. 6 illustrates some embodiments of a cross-sectional view of an integrated chip 600 comprising a disclosed integrated bio-sensor.

Integrated chip 600 comprises a sensing well 606 disposed within a top surface of the second ILD material 206. A sensing enhancement layer 604 is disposed along substantially vertical sidewalls (vertical sensing surfaces 606 v) of the sensing well 606 and along a horizontal sensing surface 606 h. The vertical sidewalls are perpendicular to a top surface of the semiconductor substrate 102. The substantially vertical sidewalls extend along multiple via layers V3, V4 and metal wire layers M3, M4 of BEOL metal stack 602.

FIG. 7 illustrates some embodiments of a cross-sectional view of an integrated chip 700 comprising a disclosed integrated bio-sensor.

Integrated chip 700 comprises a sensing well 704 disposed within a top surface of the second ILD material 206. A post 706 is disposed within the sensing well 704 at a position that is laterally disposed between sidewalls of the sensing well 704. The post 706 comprises one or more metallization layers that are electrically coupled to the horizontal sensing surface (i.e., M3) and that extend into the sensing well 704 in a direction perpendicular to the horizontal sensing 704 h surface to increase a total size of vertical sensing surfaces 704 v. For example, the post 706 may comprise a via layer V3 and a metal layer M4 that extend into the sensing well 704. The post 706 may be surrounded by a high-k dielectric layer 702, in some embodiments.

Although integrated chip 700 is illustrated as having a single post 706 extending into the sensing well 704, it will be appreciated that in other embodiments additional posts may be disposed within the sensing well 704 to further increase the sensing area (e.g., a total size of vertical sensing surfaces 704 v). For example, FIG. 8 illustrates some embodiments of a cross-sectional view of an integrated chip 800 comprising a disclosed integrated bio-sensor with a sensing well 804 having a plurality of posts, 806 a and 806 b. The plurality of posts, 806 a and 806 b, may be surrounded by a high-k dielectric layer 802, in some embodiments.

FIG. 9 illustrates a flow diagram of some embodiments of a method 900 of forming an integrated chip comprising an integrated biosensor having a sensing well with horizontal and vertical sensing surfaces.

While disclosed method 900 is illustrated and described herein as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At 902, a sensing device is formed within a semiconductor substrate. In some embodiments, the sensing device may comprise a transistor device, such as a MOS transistor, for example.

At 904, one or more lower metallization layers are formed within a first inter-level dielectric (ILD) layer. The one or more lower metallization layers are overlying and electrically connected to the sensing device. In various embodiments, the one or more lower metallization layers may comprise metal wires, contacts, and/or vias.

At 906, a middle metal wire layer is formed over the lower one or more metallization layers within the first ILD material or within a second ILD material.

At 908, a via array is formed within a second ILD material over the middle metal wire layer.

At 910, one or more additional metallization layers may be formed within the second ILD material over one or more elements of the via array.

At 912, the second ILD is selectively etched to form a sensing well that exposes a horizontal surface of the middle metal wire layer and vertical surfaces of two or more vias of the via array.

At 914, a sensing enhancement layer is formed onto exposed surfaces of the middle metal wire layer and two or more vias of the via array. In some embodiments, the sensing enhancement layer may comprise a high-k dielectric layer.

At 916, a first capping structure may be formed over the semiconductor substrate. The first capping structure comprises a first cavity, within a first side facing the semiconductor substrate, which forms a micro-fluidic channel extending over the sensing well.

At 918, a second capping structure may be formed over the semiconductor substrate. The second the second capping structure has a third cavity, facing the first capping structure, which forms a valve or peristaltic pump.

FIGS. 10-17 illustrate some embodiments of cross-sectional views showing a method of forming an integrated chip comprising an integrated biosensor having sensing well with horizontal and vertical sensing surfaces. Although FIGS. 10-17 are described in relation to method 900, it will be appreciated that the structures disclosed in FIGS. 10-17 are not limited to such a method, but instead may stand alone as structures independent of the method.

FIG. 10 illustrates some embodiments of a cross-sectional view 1000 of an integrated chip corresponding to act 902.

As shown in cross-sectional view 1000, a sensing device 202 is formed within a semiconductor substrate 102. The semiconductor substrate 102 may comprise any type of semiconductor body (e.g., silicon, SiGe, SOI) such as a semiconductor wafer and/or one or more die on a wafer, as well as any other type of semiconductor and/or epitaxial layers associated therewith. In some embodiments, the sensing device 202 comprises a MOSFET transistor having a source region 202 a, a drain region 202 b that is separated from the source region 202 a by a channel region 202 c, and a gate region 202 d separated from the channel region 202 c by a gate dielectric layer 202 e.

FIG. 11 illustrates a cross-sectional view 1100 of an integrated chip corresponding to acts 904-906.

As shown in cross-sectional view 1100, a first ILD material 204 is formed over the semiconductor substrate 102. The first ILD material 204 may comprise a low-k dielectric layer deposited by way of a vapor deposition technique (e.g., physical vapor deposition, chemical vapor deposition, etc.). One or more lower metallization layers C0-V2 are formed within a first ILD material 204 at a position overlying and electrically connected to the sensing device 202. The one or more lower metallization layers C0-V2 may comprise one or more metal wire layers, M1 and M2, configured to provide lateral interconnections or one or more metal via layers, V1 and V2, configured to provide vertical interconnections. In some embodiments, the one or more lower metallization layers C0-V2 may comprise tungsten and/or copper, for example. A middle metal layer M3 is subsequently formed over the one or more lower metallization layers C0-V2.

In some embodiments, the one or more lower metallization layers C0-V2 and the middle metal wire layer M3 may be formed by selectively exposing the first ILD material 204 to a first etchant, which is configured to selectively etch the first ILD material 204 to form a first plurality of openings. A metal material (e.g., tungsten or copper) is subsequently formed within the first plurality of openings. In some embodiments, the first etchant may comprise a dry etchant have an etching chemistry comprising a fluorine species (e.g., CF₄, CHF₃, C₄F₈, etc.). In some embodiments, the etching chemistry may further comprise oxygen or hydrogen, for example. In other embodiments, the first etchant may comprise a wet etchant comprising hydroflouric acid (HF).

In some embodiments, the one or more lower metallization layers C0-V2 and the middle metal wire layer M3 may be formed using a dual damascene process. In such embodiments, a first layer of the first ILD material 204 is deposited onto the surface of a semiconductor substrate 102. The first layer of the first ILD material 204 is then selectively etched to form a via hole and an overlying metal wire trench. After the via hole and metal wire trench are formed, a diffusion barrier layer and a seed layer are deposited within the via hole and metal wire trench. A plating (e.g., electro chemical plating) process may then be used to fill the via hole and metal line trench with metal (e.g., copper). The top surface of the first layer of the first ILD material 204 is planarized using a chemical mechanical polishing (CMP) process to remove any excess metal.

In other embodiments, the one or more lower metallization layers C0-V2 and the middle metal wire layer M3 may be formed using a single damascene process. In such embodiments, a first layer of the first ILD material 204 is selectively etched to form via holes, which are subsequently filled with a metal material (e.g., using an electro-chemical plating process). A second layer of the first ILD material 204 is then formed over the first layer. The second layer is selectively etched to form metal wire trenches, which are subsequently filled with a metal material (e.g., using an electro-chemical plating process).

FIG. 12 illustrates a cross-sectional view 1200 of an integrated chip corresponding to acts 908-910.

As shown in cross-sectional view 1200, a via array is formed within a second inter-level dielectric (ILD) material. The via array comprises a plurality of vias V3 abutting the middle metal layer M3. In some embodiments, one or more additional metal layer may be formed over the plurality of vias V3.

In some embodiments, the second ILD material 1202 (e.g., a low-k dielectric material) may be formed over the first ILD material 204 by way of a vapor deposition technique. The second ILD material 1202 is then selectively exposed to a second etchant (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) configured to selectively etch the second ILD material 1202 to form a second plurality of openings. A second metal material is formed in the second plurality of openings to form the via array and an overlying upper metal layer M4. In some embodiments, a chemical mechanical polishing (CMP) process may be used to remove excess of the second metal material from a top surface of the second ILD material 1202. In some embodiments, an upper metal layer M4 may be formed over the plurality of vias by way of a similar process. In other embodiments, one or more additional metal layers may be formed over the upper metal layer M4.

In some embodiments, the upper metal layer M4 may comprise one or more EWOD (electrowetting on dielectric) electrodes, 208 a and 208 b, and a signal output electrode 210. The EWOD electrodes, 208 a and 208 b, are configured to selectively generate electric fields that are configured to modify wetting properties of an overlying hydrophobic layer (e.g., 216) to control the flow of liquid within a micro-fluidic channel 218 a. For example, the EWOD electrodes, 208 a and 208 b, may be configured to pump fluids in a manner that fills the sensing well 214. The signal output electrode 210 is configured to provide an output signal of the sensing device 202.

FIG. 13 illustrates some embodiments of a cross-sectional view 1300 of an integrated chip corresponding to act 912.

As shown in cross-sectional view 1300, a masking layer 1302 (e.g., photoresist or a hard mask) is selectively formed over the second ILD material 1202. The masking layer 1302 defines a position of a sensing well 1304 within the second ILD material 1202. The second ILD material 1202 is selectively exposed to a third etchant 1306 (e.g., CF₄, CHF₃, C₄F₈, HF, etc.) according to the masking layer 1302. The third etchant 1306 is configured to remove the second ILD material 1202 to form a sensing well 1304 within a top surface of the second ILD material 1202.

FIG. 14 illustrates some embodiments of a cross-sectional view 1400 of an integrated chip corresponding to act 914.

As shown in cross-sectional view 1400, a sensing enhancement layer 212 is deposited. The sensing enhancement layer 212 may be deposited by way of a vapor deposition process (e.g., PVD, ALD, CVD, PE-CVD). In some embodiments, the sensing enhancement layer 212 is deposited onto interior surfaces of the sensing well 214. In some embodiments, the sensing enhancement layer 212 may also be deposited along the top surface 206 t of the second ILD material 206. In some embodiments, the sensing enhancement layer 212 may comprise a high-k dielectric material. For example, the sensing enhancement layer 212 may comprise one or more of silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), titanium oxide (TiO₂), hafnium oxide (HfO₂), tantalum pentoxide (Ta₂O₅), tin oxide (SnO), tin dioxide (SnO₂), BaxSr₁—xTiO₃ (BST).

FIG. 15 illustrates some embodiments of a cross-sectional view 1500 of an integrated chip corresponding to act 916.

As shown in cross-sectional view 1500, a hydrophobic material is deposited to form a hydrophobic layer 216 over the sensing enhancement layer 212. In some embodiments, hydrophobic layer 216 may be disposed at a position overlying EWOD electrodes, 208 a and 208 b, within the upper metal wire layer. In some embodiments, the hydrophobic layer 216 may comprise a self assembled monolayer (SAM) or a teflon material.

FIG. 16 illustrates some embodiments of a cross-sectional view 1600 of an integrated chip corresponding to act 916.

As shown in cross-sectional view 1600, a first capping structure 218 is formed over the second ILD material 206 to form a micro-fluidic channel 218 a extending over the sensing well 214. The first capping structure 218 may be formed by depositing a polymer onto a molding substrate (not shown) and then curing the polymer. For example, PDMS may be spin-coated onto a molding substrate and then heated at an elevated temperature to form the first capping structure 218. The first capping structure 218 may be subsequently transferred from the molding structure to the second ILD material 206 to form the micro-fluidic channel 218 a. In some embodiments, the first capping structure 218 may be bonded to the second ILD material 206 by way of an adhesive layer. In other embodiments, the first capping structure 218 may be bonded to the second ILD material 206 by way of a plasma activated bonding process, in which the PDMS and second ILD material 206 are exposed to a plasma (e.g., an oxygen plasma) and then brought into conformal contact.

FIG. 17 illustrates some embodiments of a cross-sectional view 1700 of an integrated chip corresponding to act 918.

As shown in cross-sectional view 1700, a second capping structure 220 is formed over the first capping structure 218 to form a chamber 222 that can act as a valve or a peristaltic pump. The second capping structure 220 may be formed by selectively etching a substrate to form a second cavity and then bonding the etched substrate to the first capping structure 218. In various non-limiting examples, the second capping structure 220 may be bonded to the first capping structure 218 by way of an adhesion layer or a plasma activated bonding process. In some embodiments, a heating element 230 may be formed between the first capping structure 218 and the second capping structure 220.

In some embodiments, the first capping structure 218 and/or the second capping structure 220 may be subsequently etched after being bonding to form one or more openings. For example, a first etching process may be performed to form a first opening 224 that extends through the second capping structure 220 and the underlying first capping structure 218 to an underlying signal output electrode 210 within the upper metal layer M4. A second etching process may be performed to form a second opening 226 that exposes the temperature sensor 228 to an ambient environment, thereby allowing the temperature sensor 228 to measure a temperature of a liquid in the ambient environment. In some embodiments, the first and second etching processes may comprise one or more of the same etching processes and/or one or more different etching processes

Therefore, the present disclosure relates to an integrated chip comprising an integrated bio-sensor having horizontal and vertical sensing surfaces.

In some embodiments, the present disclosure relates to an integrated chip, comprising a sensing device disposed within a semiconductor substrate. A back-end-of-the-line metallization stack comprising a plurality of metal interconnect layers electrically coupled to the sensing device is disposed within an inter-level dielectric (ILD) layer overlying the semiconductor substrate. A sensing well is located within a top surface of the ILD layer. The sensing well comprises a horizontal sensing surface extending along a top surface of a first one of the plurality of metal interconnect layers and a vertical sensing surface extending along a sidewall of a second one of the plurality of metal interconnect layers overlying the first one of the plurality of metal interconnect layers.

In other embodiments, the present disclosure relates to an integrated bio-sensor. The integrated bio-sensor comprises a sensing device having a transistor device disposed within a semiconductor substrate. One or more lower metallization layers are arranged within a first ILD material overlying the semiconductor substrate at a position electrically connected to the sensing device. A middle metal wire layer is arranged over the one or more lower metallization layers. A via array is arranged within a second ILD material overlying the first ILD material at a position in electrically connected to the middle metal wire layer. A sensing well is disposed within a top surface of the second ILD material and comprises a horizontal sensing surface extending along the middle metal wire layer and vertical sensing surfaces respectively extending along a via of the via array.

In yet other embodiments, the present disclosure relates to a method of forming an integrated bio-sensor. The method comprises forming a sensing device within a semiconductor substrate. The method further comprises forming one or more lower metallization layers within a first ILD material overlying the semiconductor substrate at a position electrically connected to the sensing device, forming a middle metal wire layer over the one or more lower metallization layers, and forming a via array within a second ILD material overlying the first ILD material at a position in electrically connected to the middle metal wire layer. The method further comprises selectively etching the second ILD material to form a sensing well comprising a horizontal sensing surface disposed along the middle metal wire layer and vertical sensing surfaces respectively disposed along a via of the via array.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. An integrated chip, comprising: a sensing device disposed within a semiconductor substrate; a back-end-of-the-line metallization stack comprising a plurality of metal interconnect layers electrically coupled to the sensing device and disposed within a dielectric structure overlying the semiconductor substrate, wherein the plurality of metal interconnect layers includes an overlying metal layer and a metal wire layer, and wherein the overlying metal layer is disposed over the metal wire layer; and a sensing well comprising a horizontal sensing surface extending along a top surface of the metal wire layer and a vertical sensing surface extending along a sidewall of a first portion of the overlying metal layer and a sidewall of a via disposed between the first portion of the overlying metal layer and the metal wire layer, wherein the vertical sensing surface comprises a nook located at a lower corner of the sensing well.
 2. The integrated chip of claim 1, wherein the sensing well further comprises a second horizontal surface that extends along a lower surface of the overlying metal layer.
 3. The integrated chip of claim 2, wherein the vertical sensing surface further extends along sidewalls of one or more additional metal via layers or metal wire layers overlying the metal wire layer.
 4. The integrated chip of claim 1, wherein the vertical sensing surface has vertical sidewalls that are substantially perpendicular to a top surface of the semiconductor substrate.
 5. The integrated chip of claim 1, wherein the vertical sensing surface has an angled sidewall that causes the sensing well to comprise an inverted trapezoidal shape.
 6. The integrated chip of claim 1, wherein the vertical sensing surface has one or more arches.
 7. The integrated chip of claim 1, further comprising: one or more posts disposed within the sensing well and electrically coupled to the horizontal sensing surface, wherein the one or more posts extend into the sensing well in a direction perpendicular to the horizontal sensing surface; wherein the one or more posts comprise the overlying metal layer.
 8. The integrated chip of claim 1, wherein upper surfaces of the dielectric structure and the overlying metal layer are aligned along a substantially planar surface.
 9. The integrated chip of claim 1, wherein the sensing well further comprises an opposing vertical sensing surface laterally separated from the vertical sensing surface by the horizontal sensing surface, wherein the opposing vertical sensing surface extends along a second portion of the overlying metal layer and a sidewall of a second via disposed between the second portion of the overlying metal layer and the metal wire layer.
 10. The integrated chip of claim 9, further comprising: a sensing enhancement layer disposed onto a top surface of the metal wire layer and onto the sidewalls of the via, the second via, the first portion of the overlying metal layer, and the second portion of the overlying metal layer.
 11. The integrated chip of claim 10, further comprising: a hydrophobic layer disposed onto the sensing enhancement layer at a position overlying one or more EWOD (electrowetting on dielectric) electrodes comprised within the first portion and the second portion of the overlying metal layer.
 12. The integrated chip of claim 10, wherein the sensing enhancement layer comprises a high-k dielectric film including silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), titanium oxide (TiO₂), hafnium oxide (HfO₂), tantalum pentoxide (Ta₂O₅), tin oxide (SnO), tin dioxide (SnO₂), BaxSr1-xTiO3 (BST).
 13. The integrated chip of claim 1, wherein the nook has a height that corresponds to a height of the via adjacent the vertical sensing surface.
 14. The integrated chip of claim 1, wherein the nook extends under a lower surface of the first portion of the overlying metal layer.
 15. An integrated bio-sensor, comprising: a sensing device comprising a transistor device disposed within a semiconductor substrate; one or more lower metallization layers arranged within a first ILD layer overlying the semiconductor substrate at a position electrically connected to the sensing device; a middle metal wire layer arranged over the one or more lower metallization layers; a via array arranged within a second ILD layer overlying the first ILD layer at a position that is electrically connected to the middle metal wire layer; and a sensing well comprising a horizontal sensing surface extending along the middle metal wire layer and vertical sensing surfaces respectively extending along a via of the via array from the middle metal wire layer to an overlying metal layer, wherein a vertical sensing surface has a nook positioned adjacent to the via of the via array.
 16. The integrated bio-sensor of claim 15, further comprising: a sensing enhancement layer disposed onto a top surface of the middle metal wire layer and onto sidewalls of the via of the via array.
 17. A method of forming an integrated bio-sensor, comprising: forming a sensing device within a semiconductor substrate; forming one or more lower metallization layers within a first ILD layer overlying the semiconductor substrate at a position electrically connected to the sensing device; forming a middle metal wire layer over the one or more lower metallization layers; forming a via array within a second ILD layer overlying the first ILD layer at a position that is electrically connected to the middle metal wire layer; and selectively etching the second ILD layer to form a sensing well comprising a horizontal sensing surface disposed along the middle metal wire layer and vertical sensing surfaces respectively disposed along a via of the via array from the middle metal wire layer to an overlying metal layer, wherein the etching of the second ILD layer forms a nook in the sensing well adjacent to the via of the via array.
 18. The method of claim 17, wherein the vertical sensing surfaces of the sensing well are disposed along the overlying metal layer.
 19. The method of claim 17, further comprising: depositing a high-k dielectric film onto interior surfaces of the sensing well.
 20. The integrated chip of claim 9, wherein the first portion of the overlying metal layer has a first sidewall facing the sensing well that has a first slope and the second portion of the overlying metal layer has a second sidewall facing away from the sensing well that has a second slope that is different than the first slope. 